TREX set up and Knowledge Articles

Hello Experts,

Am trying to create Knowledge Articles on system, where am able to save KA's & if i try searching for the KA's system throwing rror as" Check Trex setup"

Now my question is:

1. Where can i check in system that TREX set up is there in the system or not

2. which version i have to (currently am using 7.0)

3. if TREX has to be set up on system what should i do

4. what are the RFC required for TREX set up, what kind of values to be given in TREX

Help me with additional information also, if am missing any thing, and which is useful for creating KA's

Thank u in advance